The introduction of both new surgical devices and reengineered existing devices leads to modifications in the way traditional tasks are carried out and allows for the development of new surgical techniques. Each new device has benefits and limitations in regards to tissue interactions that, if known, allow for optimal use. However, most surgeons are unaware of these attributes and, therefore, new device introduction creates a &#;knowledge gap&#; that is potentially dangerous. The goal of this review is to present a framework for the study of device&#; tissue interactions and to initiate the process of &#;filling in&#; the knowledge gap via the available literature. Surgical staplers, which are continually being developed, are the focus of this piece. The integrity of the staple line, which depends on adequate tissue compression, is the primary factor in creating a stable anastomosis. This review focuses on published studies that evaluated the creation of stable anastomoses in bariatric, thoracic, and colorectal procedures. Understanding how staplers interact with target tissues is key to improving patient outcomes. It is clear from this review that each tissue type presents unique challenges. The thickness of each tissue varies as do the intrinsic biomechanical properties that determine the ideal compressive force and prefiring compression time for each tissue type. The correct staple height will vary depending on these tissue-specific properties and the tissue pathology. These studies reinforce the universal theme that compression, staple height, tissue thickness, tissue compressibility, and tissue type must all be considered by the surgeon prior to choosing a stapler and cartridge. The surgeon&#;s experience, therefore, is a critical factor. Educational programs need to be established to inform and update surgeons on the characteristics of each stapler. It is hoped that the framework presented in this review will facilitate this process.
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The objective of this review is to emphasize the framework for the study of device&#;tissue interactions and to initiate the process of &#;filling in&#; this framework with data from the available literature concerning surgical staplers. Examples of studies that describe surgical stapler&#;tissue interaction in bariatric, colorectal, and thoracic procedures are mentioned and referenced in this paper; however, an in-depth discussion of these topics that takes into consideration all published studies is beyond the scope of this review. In addition, more detailed information regarding individual staplers and their evolution, as well as the difference between the products of different manufacturers, can be obtained from the various companies and the literature.
Although these questions appear to be straightforward (see ), to date, there are little to no published scientific data regarding the various tissue and device interactions and thus no definitive answers to these questions. Developing a deeper foundation to solve these issues will require a collective effort to gather, collate, and organize the available data. This effort will also require widespread collaboration between physicians, scientists, and engineers from both clinical practice and the medical device industry. Ideally, a systematic research program and subsequent educational programs would help to fill the educational gap that exists for most practicing surgeons and, very importantly, in surgical training. 4
The first consideration in this simple framework pertains to the specific type of device used. Surgeons must know the basic unit used by the device (eg, staple in a stapler), the desired outcome (eg, create an anastomotic staple line), and the type of device that will perform the function (eg, stapler). The second consideration is the relevant properties of the tissue that affect its interaction with the device. Finally, the biomechanical interaction between tissue and device must be considered. An example of potential research questions regarding these device&#;tissue interactions for staplers is shown in .
The surgical stapler is an example of a device that is commonly used during surgical procedures and, at the same time, is in an almost constant state of developmental evolution. Although these devices are highly versatile and efficient, there have been well-documented incidences of staple line leaks leading to postoperative complications that often resulted from issues not attributable to ischemia. 2 Of these, technical errors can play a significant role, potentially increasing the risk of bleeding, transfusions, and unplanned proximal diversions, particularly in gastrointestinal procedures. 1 , 3 Many surgeons are not aware of the tissue handling characteristics and limitations of new or reengineered staplers, and thus there is a knowledge gap that can impact the clinical outcome of operations. To improve surgeons&#; understanding of staplers and stapler&#;tissue interactions with the goal being to optimize the clinical outcome and fill this knowledge gap, a framework is needed within which the existing literature can be reviewed and the available data gathered and made accessible ( ).
An unintended consequence of these rapid technological advances is the production of a collective &#;knowledge gap&#; in surgeons&#; understanding of how devices interact with tissue. In many cases, surgeons may not understand either the scientific/clinical basis for the optimal use of these devices or how to optimally take advantage of unique intricacies inherent to a particular device. Consequently, surgeons may often fall back on their own experience, exercise their own judgment, or rely on anecdotal evidence, which may translate into suboptimal patient outcomes, even if the devices themselves function correctly. 1
Technological advances across numerous scientific disciplines have produced many unique surgical devices and instruments that are used during surgery. Both the ongoing introduction of new devices and continuing technical improvements in existing devices are changing the way surgeons perform traditional tasks and enabling them to develop new surgical techniques with the goal of improving patient outcomes.
When trying to decrease anastomotic leak rates for instance, Çakabay et al emphasized the importance of meticulous technique and suggested a protocol-driven approach. 35 Additional studies also support the concept that a surgeon&#;s experience with a given device is a key determinant in patient outcomes. A review of operative reports and web-based charts for colon and rectal resections at Brigham and Women&#;s Hospital (Boston) found that 19% of these procedures featured a technical error involving the stapling device. 1 Errors included (but were not limited to) surgeon misfiring, incomplete anastomosis (inadequate donuts, staple line defects, or primary device failure), and were associated with a significantly (P<0.03) increased risk of gastrointestinal bleeding, transfusions, and unplanned proximal diversions. Similarly, a review published over two decades ago of anastomoses made during esophageal resections at the Royal Victoria Hospital (Belfast) concluded that although stapling devices brought uniformity to the creation of anastomoses, they &#;cannot compensate for deficiencies in surgical technique&#; and further commented that advances in technology &#;cannot overcome deficiencies in technique such as indelicate handling of the tissues, tension on anastomoses, ischemic anastomoses, and the attempted salvage of unsatisfactory anastomoses rather than takedown and construction of a second anastomosis&#;. 36
As shown, many device-associated variables, such as stapler diameter, staple size, tissue location, and compression time as well as tissue variables (ie, tissue thickness and compressibility), can affect the integrity of the staple line and patient outcomes. However, all these factors must be considered in the context of perhaps the most relevant variable: the experience and surgical technique of the surgeon.
Similar, albeit less formal, efforts have been undertaken for surgical stapling. McColl et al created a multiple-choice test to assess general surgery residents&#; knowledge on the purpose and function of linear, circular, and laparoscopic staplers. 34 The test was administered both before and after a 40-minute didactic teaching lecture delivered through a collaborative effort between an attending general surgeon and industry representative with comprehensive knowledge of stapling devices. Mean test scores significantly increased from 53% (pretest) to 77% (posttest), (P<0.05). In this small group (n=26), this study again identifies a significant gap in existing stapling knowledge and showed the feasibility and value of industry&#;surgeon collaboration to develop an effective educational program for clinicians.
Formal testing has recently revealed that there are knowledge gaps in many surgeons&#; understanding of the safe use of many commonly used medical devices. Such deficiencies have led to the creation of educational programs. For instance, The Society of Gastrointestinal and Endoscopic Surgeons has begun to fill this gap for energy devices with a well-developed online curricula, a textbook (Fundamental Use of Surgical Energy&#;), and a validated examination based on content derived from the collaboration of health care professionals and representatives from industry. 32 , 33
In addition to the magnitude of the compressive force, compression time is another important variable. Using a linear stapler, Nakayama et al showed in stomach tissue that there was a relationship between the amount of time a tissue was compressed and optimal (defined as a well formed closed staple) staple formation. 30 Increasing precompression times both decreased staple height and increased optimal staple formation rate. In a separate study, Nakamura et al reported that prolonged perifiring compression with a linear stapler effectively prevented pancreatic fistula formation and reduced the length of stay following laparoscopic distal pancreatectomy. 31 It is important to note that while compression is a key factor in maintaining staple line integrity, excessive compression must be avoided to prevent ischemia and tissue destruction. 2
Numerous studies performed with various tissue types (gastric, 28 colorectal, 1 and pancreatic 29 ) provide data that demonstrate the importance of a surgeon&#;s familiarity with tissue thickness and compressibility in order to optimize stapler&#;tissue interaction. The most robust papers examining the relationship between outcomes and compression come from the bariatric literature, where the results obtained with staples of different lengths have been compared. Three studies which collectively assessed more than 4,000 patients came to the same conclusion; namely, that more compression is advantageous and that a smaller staple height was associated with a lower incidence of hemorrhage and stenosis/stricture. 24 , 26 , 27 The largest of these studies also noted a trend toward a decreased leak rate in the shorter staple subgroup. 24
The mechanical properties of tissues are also influenced by inherent patient differences including specific tissue location, accessibility, comorbidities, prior medications/therapy, and the pathological condition of the tissue. Differences in the profile for each patient in regards to this list of variables not only influence the tissue thickness but also its compressibility. For example, the changes in thickness associated with irradiation may alter the inherent compressibility of the tissue. As the tissue becomes less compressible, an increased amount of pressure needs to be applied by the stapler to the tissue to ensure that the desired closed staple height is obtained. All stapler reloads are indicated for a specific closed staple height; the tissue is also compressed to the same height. Surgeons must be aware that the choice of staple cartridge (staple height) will determine the amount of compression imparted upon the tissue when the stapler is closed and fired.
There are published data concerning device&#;tissue interactions that demonstrate the importance of the biomechanical factors and variables mentioned above, including compression. As early as the s, Astafiev&#;s experiments with stapling devices of his era demonstrated that &#;The defined values of isolated organ walls cannot serve as initial data for estimation of suturing gap range in instruments, for they do not include the tissue turgor that depends on blood filling, tissue fluid pressure, and other factors.&#; 23 Consequently, each tissue type must be appropriately compressed before suturing or stapling to achieve the optimal amount of perfusion and homeostasis for healing. More recent studies lend further support to the concept that increased compression is associated with desirable outcomes: lower leak rates, 24 increased intraluminal pressure, 25 improved hemostasis, 24 and minimized wound contraction, potentially leading to decreased stricture rates. 24 , 26 , 27
It is important to realize that the principles of tissue biomechanics that are important for stapling also apply to hand sewn anastomoses. 22 One of the critical biomechanical variables to consider when joining two tissues together is the degree of compression applied. The optimal amount of compression for a particular tissue will largely depend on the tissue&#;s mechanical properties. The biphasic nature of human tissue, its inherent compressibility, and differences in thickness all work together to produce a viscoelastic response when tissue is placed under a compressive force. Consequently, tissue properties will change over time as the tissue is compressed, resulting in changes such as tissue elongation and stress relaxation. 2 In addition to the impact of tissue thickness on compression, the inherent elasticity of the tissue in question is also an important variable. 2 The force and duration of compression ideally will result in optimal tissue compression and elongation such that the staple line will be hemostatic and well perfused without the development of tissue shearing. 2
The unique properties of the different types of tissues in the body have a major impact on the choice of a stapler and staple height. Different tissues in the body vary in thickness, and dimensions may change based on sex, age, organ/system/anatomical structure, age, location within an organ, preoperative therapies, intraoperative medications, and the disease state. Furthermore, tissue has a biphasic nature due to having both liquid and solid properties, and different tissue types have inherently different ratios of liquid and solid components as well as air components. In addition to these intrinsic mechanical tissue properties that help to differentiate tissue, intrinsic biochemical properties such as the protein content and metabolic profile are also differentiating factors. Moreover, the extrinsic blood supply will also vary by tissue type and contributes further to differentiation. The compressive load necessary to form a stable anastomosis will depend on these inherent tissue properties, as well as the current physical condition of the tissues to be joined, and is of paramount importance for achieving adequate perfusion and healing as well as to limit ischemia/tissue destruction. Optimal stapling of any tissue requires an adequate tissue compression time (to decrease the fluid in the tissue) to allow elongation of the tissue being compressed, smooth firing of the instrument, and consistent staple line formation; this need must be balanced against the risk of increased tissue tearing and excessive tensile strength. 2
An example of how the choice of a particular stapler might affect surgical outcomes can be seen if the circular end to end anastomotic stapler is considered. These devices come in different diameter sizes to accommodate the variety of bowel lumen diameters encountered clinically. The effect of circular stapler lumen diameter (not staple size) on outcomes is still a matter of debate. Our literature search found 17 publications addressing this topic; 5 &#; 21 however, many of the outcomes measures considered (hemorrhage, leak, weight loss) were not significant or did not show consistent trends from study to study. For example, Kim et al reported that use of a 25 mm diameter circular stapler was a risk factor for gastric stasis during the early postoperative period (eg, 6 months) when compared to results obtained with a 29 mm diameter circular stapler. However, the 29 mm stapler was found to be a risk factor for bile reflux, gastritis, and esophagitis in the late postoperative period (eg, 12 months). 5 Of note, prior studies did not show significance in regards to these or similar outcomes measures. The only exception to this lack of concordance is that there was a consistent trend across 12 studies towards increased stenosis and stricture with a smaller lumen stapler. Thus, the clinical data are often very difficult to interpret; the ideal stapler type may vary based on which outcome measure is assessed (stenosis versus bile reflux).
Staples in surgical staplers are made available in various sizes and heights ( ) so that the surgeon can choose the one that provides appropriate homeostasis/tissue apposition without significant ischemia or tissue destruction. 2 If the closed staple height is too high, then it may inadequately appose the tissues and result in leakage, bleeding, and/or dehiscence. Conversely, if the staple height selected is too low, then ischemia, serosal shearing, or &#;cheese wiring&#; may result, potentially leading to leakage or frank necrosis. There are at least three staple heights for most linear staplers. Presently, it is our experience that staple selection is largely based on anecdotal evidence and the practices of attending surgeons passed down from teacher to student at each institution.
Most modern staplers bend each staple into a B-shape staple form, which helps to secure the tissue in place. However, malformed staples can occur because staple leg bending depends on a number of tissue/stapler characteristics including tissue thickness, tissue viscosity, staple height, and other staple properties (thickness, bending characteristics, type of metal, etc). Staples are designed to form consistently, and staples that are not forming as intended should be investigated. provides examples of acceptable and unacceptable staple forms, as determined by a staple manufacturer (note that staplers should always be used in accordance with published indications and contraindications).
While the modern surgical stapler can be traced back to the work of Humer Hültl in the early s, today&#;s instruments are markedly different, largely due to the work of innovators such as von Petz and Ravitch. 3 Unlike the original devices, modern staplers are most often single-use instruments (advantageous from the viewpoint of sterility). Also, staplers have been developed for use in either open or minimally invasive procedures.
We focused primarily on studies that reported data from relatively smaller patient populations because these studies typically disclosed the specific devices used during the surgical procedure, whereas larger patient studies often did not report this information as they generally focused on the surgical techniques.
A search of the medical literature using MEDLINE ® , EMBASE&#;, and the Knovel ® Technology Database was conducted for the period of January &#;November to identify published articles and electronic book chapters related to surgical device&#;tissue interactions, surgical staplers, and the use of surgical staplers in thoracic, bariatric, and colorectal surgical procedures. The full articles were retrieved and manually filtered in order to identify relevant articles. Additional references were identified from the reference lists of the filtered articles.
Staple line integrity is a major priority in bariatric surgery. Leaking staple lines and hemorrhage are associated with considerable morbidity and, in some cases, mortality. The overall incidence of bariatric surgical complications is reported to be <10% and the incidence of postoperative bleeding about 3%.37 The incidence of potentially life-threatening, permanently disabling, or fatal complications varies depending on the particular procedure done; for gastric bypass surgery, sleeve gastrectomy, and adjustable gastric band, the rate of these types of complications are 3.6% versus 2.2% versus 0.9%, respectively (P<0.001 for all).38
When considering device&#;tissue interactions in the field of bariatric surgery, a strong familiarity and understanding of the stomach is of critical importance. The stomach is an example of an organ whose tissue thickness varies considerably from location to location; this characteristic will influence the performance of staplers. Mean stomach wall thickness measurements range from 1.6 to 3.1 mm (maximum values range from 2.2 to 4.5 mm), with thickness typically increasing as one moves from the esophageal gastric junction to the pylorus. Moreover, thickness is reduced along the axis of the stomach and toward the greater curvature versus the lesser curvature.28
The varying tissue thickness of the stomach mandates that the surgeon carefully consider the specific location of the planned staple line, as this will influence the choice of staple size.28 For example, use of a staple that is &#;too small&#; in the prepyloric region of the stomach can lead to excessive tissue compression or inadequate staple formation. This could ultimately lead to tearing of the tissue or even staple line failure. Thus, it may not be surprising that, in the authors&#; experience, most surgeons use staples with longer leg heights when stapling on the distal stomach as compared to the more proximal stomach.
The importance of choosing the most appropriate staple size was demonstrated in a retrospective study of patients who had laparoscopic Roux-en-Y gastric bypass surgery. Patients who had an anastomosis constructed with a circular stapler (Covidien EEA ; 25 mm diameter anvil; Mansfield, MA, USA) that fired staples having a 3.5 mm open staple height had a significantly lower rate of stricture requiring dilatation than those in whom a circular stapler (Covidien EEA25; 25 mm diameter anvil) firing staples with 4.8 mm open staple height was utilized (6.1% versus 15%, P=0.01). Of note, the rate of leakage and abscess formation for the small and large staple anastomoses was similar.26 A larger study comparing a series of 1,074 patients who had undergone Roux-en-Y gastric bypass using a circular stapler (Covidien DST Series EEA; 25 mm diameter anvil) that fired staples with a 3.5 mm open staple height with another series of 2,606 patients treated using a circular stapler (Covidien Premium Plus CEEA; 25 mm diameter anvil) firing staples with a 4.8 mm open staple height noted significantly lower rates of hemorrhage (0.37% versus 2.45%, P<0.001) and insignificantly lower rates of leak and stenosis for the smaller staple size group.24 It is important to note that these results demonstrate an association between staple size and outcome; however, since the studies were not randomized and because the tissue thickness in each case is unknown, it is not possible to attribute the improved results to the use of the smaller staple height. It should be mentioned that the main difference between the circular staplers on the market presently is that the Covidien EEA has a fixed open staple height of 3.5 mm (closed staple height 1.5 mm) or 4.8 mm (closed staple height 2.0 mm) whereas the Ethicon CDH (Ethicon Inc., Somerville, NJ, USA) has a variable staple height range (ie, open staple height of 5.5 mm with a gap setting that can be adjusted to control for a closed staple height from 1.0 to 2.5 mm). The abovementioned studies emphasize the importance of understanding the relationship of tissue compression with closed staple height.
In colorectal surgery, anastomotic leakage (reported incidence varying from 0 to as high as 30%39) is a major issue due to the increased risk of associated complications, the potential need for additional operative procedures, extended hospital stays, and increased morbidity and mortality rates. Anastomotic leakage rates vary from the colon to the rectum, with much higher rates in the rectum. Anastomotic leaks may affect long-term outcomes and have been associated with an increased prevalence of locoregional recurrence in cancer patients40,41 and poor functional results in patients undergoing low anterior resection.42
As in bariatric surgery, tissue thickness is an important consideration in colorectal cases. The normal uncompressed thickness of the small intestine wall typically measures between 1 and 2 mm (distended lumen), whereas the colon wall may be up to 3 mm thick (distended).43 Bowel wall thickening can occur in pathological situations. Mild thickening of <2 mm may occur from infectious enterocolitis, ulcerative colitis, Crohn&#;s disease, radiation injury, ischemia, diverticulitis, edema, or submucosal hemorrhage. More marked thickening of >2 mm can result from adenocarcinoma, gastrointestinal stromal tumor, metastases, lymphoma, severe colitis, severe diverticulitis, or systemic lupus erythematosus.43 As observed for other tissues, understanding how these conditions can influence properties such as tissue thickness and compressibility is paramount if the surgeon is to select the most appropriate anastomotic method (staple versus hand sewn), and if a stapled anastomosis is to be constructed, the best stapler (linear versus circular) and staple height to obtain the best possible surgical outcome.
Anastomosis following rectal resection presents the surgeon with the additional technical challenge of rejoining the bowel deep in the pelvis, where access is difficult because of the bony confines. Further, linear transection of the distal rectum to remove the specimen is also quite challenging, especially in the narrow, deep male pelvis. When using laparoscopic methods, two or more staple firings may be required to transect the rectum. Further, because it is difficult to place the linear staplers at right angles to the axis of the rectum in the deep pelvis, the staple line may be long and oblique; at least one author suggests that this issue may increase the risk of anastomotic leak.44
Curved or radial staplers have been developed as an alternative to the standard straight, linear stapler to facilitate division of the distal rectum. These staplers have gently arched end effectors, and the final result is a curved staple line. The slightly rounded stapler head has a narrower profile than a standard linear stapler of the same length, and this feature facilitates placement of the device into the deep pelvis, while preserving staple line length. This type of stapler lays down three rows of staples and transects the rectum between the second and third staple rows. This obviates the need to manually divide the rectum with a scalpel after using a standard transverse stapler (eg, Ethicon PROXIMATE® TX or Covidien DST Series&#; TA type). Mari et al integrated the use of a curved stapler into their procedure for laparoscopic lower anterior rectal resections,45 and they reported no intraoperative or postoperative bleeding and only two leaks among the 45 patients in the series.
A patient&#;s comorbidities can influence tissue properties and should be taken into consideration. For instance, it is well known that diabetes mellitus can change the microvascular properties of the tissue and that corticosteroid use is associated with a higher rate of anastomotic leaks. If the thickness of the bowel is impacted by these comorbidities, then the surgeon should recognize this fact and make the selection of staple height and technique (hand sewn versus stapled) with this in mind. However, it is not clear if, and how, specific comorbidities affect tissue compressibility or elasticity. Presently, surgeons may choose to proximally divert the higher risk patient with multiple comorbidities after constructing an anastomosis in order to lower the chance of a symptomatic leak forming. Although there are no supportive data or guidelines presently, it seems reasonable to take comorbidities into account when attempting to predict a given device tissue interaction.
Other risk factors for anastomotic leakage after laparoscopic intracorporeal colorectal anastomosis ( ) have been published. Kim et al reviewed patients over a 2-year period who had undergone laparoscopic sigmoidectomy and anterior resection using a double-stapling technique for distal sigmoid and rectal cancers.15 In this series, they found that repeated applications of linear staplers to transect the rectum distally was a significant risk factor (P=0.04) for anastomotic leakage. Furthermore, in a univariate analysis, the use of circular staplers with large diameters (ie, 31 and 33 mm) was associated with a significantly higher rate of anastomotic leakage after laparoscopic rectal transection versus results with the smaller diameter staplers (P=0.022). The authors speculated that a larger diameter circular stapler may cause the distal remnant rectum to be more distended and, consequently, make the rectal wall thinner and decrease blood supply to the stapled anastomosis.
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To emphasize the importance of proper surgical training and experience in achieving good surgical outcomes, Detry et al published a review of 1,000 consecutive colorectal anastomoses performed by a single surgical team between and and suggested that stapled anastomoses were safe and reliable if the staplers were properly utilized and the steps of the procedure standardized.46 Several authors report that procedural innovation and a fundamental understanding of surgical stapling devices are important in achieving good patient outcomes.45,47
Vital structures, such as the pulmonary arteries, bronchi, and the vagus nerve and its branches, must be considered when using staplers in the chest.
Similar to colorectal and gastric tissues, lung tissue also varies in thickness and compressibility. The inherent air content of the lungs make them even more variable in thickness than many other tissues. Difference in tissue properties also extend to the biochemical makeup of lung tissue. For instance, it is known that lung tissue has a natural elasticity due to its higher proportion of elastin. This affects the tissue&#;s properties and likely changes it viscoelastic behavior and, consequently, the ideal compression time and degree of compression.
To this end, the location of the lesion within the lung must be taken into account. For example, if stapling is performed in the periphery of the lung, where there is more air than solid or liquid components, then adequate compression requires less pressure and a shorter prefiring compression time. In contrast, the more centrally located lung tissue contains more fluid (blood) and solid components (bronchial cartilage). Consequently, longer compression times and taller staples are required to obtain a well formed staple line and to maintain staple line integrity.48
Another variable is the pathological state of tissue, ie, diseased or normal. Increases in thoracic tissue thickness are observed for a number of pathological conditions including lung carcinoma, pulmonary fibrosis, and asbestosis. Conditions such as emphysema and tuberculosis can also affect tissue and outcomes. For example, emphysematic tissue is often characterized as containing less protein, which can make it more difficult to achieve aerostasis.49 In fact, Hunt and Aye showed that patients with emphysema are at the highest risk of air leak.50 Furthermore, because of destruction of connective tissue and increased compliance, there may be an increased risk of tissue tearing adjacent to staple lines,51 which may delay healing after surgery.52
The development of a bronchopleural fistula is a major complication associated with thoracic surgery. Although the incidence of these fistulas after pneumonectomy is reported to be lower after stapling (2.0%&#;5.2%) versus hand suturing (6.6%&#;18.2%),53 techniques to further reduce the rate of fistula formation would, if successful, improve patient outcomes. Aoki et al noted that when fistulas develop after stapling the main bronchus, the specific site of the fistula is the stump&#;s center; they hypothesized that there was increased tension in the membranous part of the bronchus in this location due to compression by the stapler.53 They conducted a small study in patients undergoing pneumonectomy wherein the conventional procedure was modified by folding both sides of the cartilaginous wall while stapling, thereby reducing the tension, and then not covering the stump afterwards. None of the patients developed a fistula although a larger study is required to confirm these results.
The introduction of video-assisted thoracic surgery (VATS) methods over the past 20 years has greatly changed thoracic surgery. VATS methods allow for minimally invasive treatment of benign and malignant pulmonary lesions, lung volume reduction surgery, decortication, mediastinal mass removal, evacuation of fluid or infectious tissue from the pleural cavity, and diaphragmatic plication. Compared with open procedures, the benefits of VATS include shorter hospital stays and less postoperative pain, morbidity, narcotics usage, and scarring.54&#;57 Unfortunately, there are minimal published data specific to device&#;tissue interactions in this area. What is clear, however, is that technique still matters.
A review of all thoracoscopic procedures performed by Gossot et al over a 1-year period was conducted to determine the rate of adverse events related to the use of an endostapler during VATS.58 Both a database and recorded videotapes of the procedures were evaluated. Their review of 434 staple firings carried out on 130 patients showed that some adverse events were attributed to surgical errors; however, others were attributed to the stapling device, ie, oozing (13 cases), active hemorrhages on staple line (five cases), partial or total disruption of the staple line (13 cases versus one case), and technical device malfunctions (two cases).58 They determined that 34 out of 434 (7.6%) stapler firings resulted in a minor or major problem; this incidence is higher than that noted in patients undergoing similar open thoracic operations. In 12 cases, no specific action was required, whereas in 22 cases the resulting problem mandated repair. They speculated that there were three reasons for the increased incidence of stapler-associated problems in VATS versus open lung resection: 1) indecision in choosing between the 3.5 and 4.5 mm staple height due to difficulty in appreciating both the thickness and resistance of lung tissue in the minimally invasive setting, 2) the relatively small jaw opening of endostapler can make loading of the tissue difficult and may create friction and lead to tearing of the tissue, and 3) difficulty in precisely positioning the stapler tip may result in excessive traction being placed on the tissue.58 A key message was that adverse events were attributable to both surgical errors as well as device-related errors. Training and educational programs should help to reduce the incidence of surgical errors, whereas improvements by manufacturers in staple design would help reduce device errors and complications.
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Ethical approval will not be required because this proposed systematic review and meta-analysis is based on previously published data, which does not include intervention data on patients. The findings of this study will be submitted to a peer-reviewed journal and will be presented at a relevant congress.
PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI) and Wanfang Databases will be comprehensively searched from January to July . All eligible randomised controlled trials (RCTs), non-RCTs or observational studies comparing the two types of staplers will be included. A meta-analysis will be performed using Review Manager V.5.3 software to compare the safety and efficacy of linear and circular staplers for oesophagojejunostomy in TLTG. The primary outcomes are anastomotic leakage, anastomotic stricture, anastomotic haemorrhage. The secondary outcomes include time to first instance of passing gas after surgery, first feeding time, total operation time, reconstruction time, estimated blood loss. The heterogeneity of this study will be assessed by p values and I 2 statistic. Subgroup analyses and sensitivity analyses will be used to explore and explain the heterogeneity. The risk of bias will be assessed using the Cochrane tool or the Newcastle-Ottawa Quality Assessment Scale.
Total gastrectomy is often recommended for upper body gastric cancer, and totally laparoscopic total gastrectomy (TLTG) is deemed to be a promising surgical method with the well-known advantages such as less invasion and fast recovery. However, the anastomosis between oesophagus and jejunum is the difficulty of TLTG. Although staplers have promoted the development of TLTG, the choice of suitable staplers to complete oesophagojejunostomy is controversial and unclear. Therefore, a higher level of research evidence is needed to compare the two types of staplers in terms of safety and efficacy for oesophagojejunostomy in TLTG among patients with gastric cancer.
Therefore, the choice of staplers for complete oesophagojejunostomy of TLTG is still an unclear and controversial topic. 7 8 14 Majority of the previous comparisons on contrasting linear and circular stapling anastomosis for oesophagojejunostomy in TLTG are retrospective and are based on small-sample studies, further, the results from such investigation have been inconsistent and even contradictory. Therefore, the safety and efficacy of linear stapling anastomosis has not been well resolved in these studies and remains to be confirmed by higher-level evidence. In view of this, a systematic review and meta-analysis will be conducted based on relevant published literature to further explore and compare the safety and efficacy of the linear stapler and circular stapler in TLTG, with the hope of providing a reference to help surgeons choose a suitable stapler.
However, the anastomosis and reconstruction of oesophagojejunostomy is the focal point and difficulty of totally laparoscopic total gastrectomy (TLTG). 6 Presently, the two commonly used anastomosis methods for oesophagojejunostomy are circular stapler anastomosis and linear stapler anastomosis. 6&#;8 Considering the characteristics of laparoscopic surgery, traditional circular anastomosis has certain inherent limitations. For example, the circular stapler cannot be placed through a trocar, and it needs to be placed in the abdominal cavity through a small assisted incision in the abdomen, thereby reducing the benefit of laparoscopic surgery. Although OrVil does not pass through the abdominal cavity, a top-down placement method is required, but the operation requires an anaesthesiologist to cooperate. 9 Compared with the circular stapler, linear stapler has some advantages in oesophagojejunostomy. 10 For example, it can easily enter the abdominal cavity through the trocar, without purse-string suture, and the used instrument is easy to operate. The primary disadvantage of linear anastomosis is the need for a long-enough oesophageal stump for anastomosis, which limits the surgical margin and could increase the tension of the anastomosis. For this reason, some scholars consider that linear anastomosis is not appropriate for patients with tumours located in the upper stomach or close to the oesophagogastric junction or tumours with oesophageal invasion. 11 12 A meta-analyses comparing linear anastomosis with circular anastomosis in laparoscopic distal gastrectomy (LDG) suggested that linear anastomosis is better than circular anastomosis in LDG. 13 However, considering the differences between TLTG and LDG in terms of surgical methods, surgical objects and surgical difficulties, this conclusion cannot be applied to guide the implementation of TLTG.
Gastric cancer is a common malignant tumour of the digestive tract, and its morbidity and mortality ranked fifth and third, respectively, among the global malignant tumours. 1 Although the overall incidence of gastric cancer has been decreasing worldwide, the incidence of upper body gastric cancer has been on an increasing trend. 2 3 Radical resection is the only curative modality recommended for primary treatment of patients with resectable gastric cancer, and total gastrectomy is often performed for upper body gastric cancer. 3 4 Laparoscopic technique is one of the main development direction of surgical treatment for gastric cancer. The results of a multicentre retrospective cohort study have shown that laparoscopic total gastrectomy (LTG) could achieve comparable oncological outcomes to open total gastrectomy. 5 Furthermore, with the development of new laparoscopic equipments and the accumulation of advanced experience in the application of laparoscopic techniques, laparoscopic surgery for gastric cancer has undergone a technological transition from laparoscopic-assisted surgery to totally laparoscopic surgery which is less invasive and expedites postoperative recovery. 6
Ethical approval will not be required because this proposed systematic review and meta-analysis is based on previously published data, which does not include intervention data on patients. The findings of this study will be submitted to a peer-reviewed journal and will be presented at a relevant congress.
In order to ensure the robustness and reliability of evidence, sensitivity analysis will be performed to assess the effect of studies with a high risk of bias. The results will be compared to decide whether low-quality studies should be excluded based on sample size and quality assessment of studies or effect on pooled effective size. In addition, a leave-one-out sensitivity meta-analysis might be considered if a study involving a large number of patients was based on different types of studies. 25
The potential publication bias will be investigated using funnel plots drawn by the STATA SE V.12.0 software. The publication bias will be assessed by visual inspection of the Begg&#;s funnel plots, whereby, if the SE of logOR of each study is plotted against its logOR, an asymmetric plot suggests a possible publication bias. 23 In addition, the asymmetry of the funnel-plot will be assessed using the Egger linear regression test at the p<0.10 significance level. 24
All the meta-analyses will be performed using Review Manager V.5.3 (Cochrane Collaboration, Oxford, UK). The WMD and OR will be used to compare continuous and dichotomous variables, respectively, and all the results will be reported with 95% CIs. For the literature reporting median and range of continuous variables, the mean and SD will be extracted using the method described by Hozo et al. 21 Continuous variables that only provided quartiles or mean and SD could not be extracted will be eliminated. Assessment of statistical heterogeneity among the studies will be undertaken using the χ 2 and I 2 statistical tests. Where there is no obvious statistical heterogeneity among the studies as denoted by a p value &#;0.1 or I 2 &#;50%, the fixed effect model will be used for meta-analysis. Conversely, in cases where statistical heterogeneity is observed among studies with a p value <0.1 or I 2 >50%, a random effect model will be used for meta-analysis. If concerns for high heterogeneity (I 2 value >75% indicates high heterogeneity) 22 exist, a sensitivity analysis will be performed.
The quality of the studies will be independently scored by three reviewers using the Cochrane risk of bias tool or the Newcastle-Ottawa Quality Assessment Scale (NOS). 19 The methodological quality of RCTs will be assessed using the Cochrane risk of bias tool. 20 The methodological quality of non-random studies such as case&#;control and cohort studies will be assessed by the NOS, which consists of three factors: patient selection, comparability of the study groups and assessment of outcome. A score of 0&#;9 (allocated as stars) will be allocated to each study except for RCTs. RCTs and observational studies achieving six or more stars will be considered to be of high-quality studies. In cases where discrepancies arose, studies will be re-examined and a consensus will be reached through discussion.
Three reviewers will independently extract the data, and any discrepancy will be resolved by discussion until a consensus is reached. All extracted data will be filled in data extraction sheets created by Microsoft Excel (Microsoft Corporation, Redmond, Washington, USA). The main extracted information are as follows: (1) study characteristics (eg, first author&#;s name, year of publication, country of study, study design, study period, number of patients, number of patients with linear stapler, number of patients with circular stapler); (2) participant characteristics (eg, age, sex, ethnicity, body mass index (BMI), cancer stage, American Society of Anesthesiologists (ASA) score); (3) primary outcomes: anastomotic leakage, anastomotic stricture, anastomotic haemorrhage, total postoperative complications; (4) secondary outcomes: time to first instance of passing gas after surgery, first feeding time, total operation time, reconstruction time of digestive tract, estimated blood loss, lymph node harvest, the distance from the proximal margin of the tumour, postoperative hospital stay. Any missing information is supplemented by contacting the original author by or .
Any duplication will be identified and removed using the EndNote X8 reference management software (Clarivate Analytics, Thomson Place, Boston, USA). Under the pre-established inclusion and exclusion criteria, the titles and abstracts of all remaining literatures are carefully read and examined to exclude obviously unrelated documents. The full text of the screened literature will be deeply and carefully read to determine whether it is to be included. All steps will be independently conducted and cross-checked by three reviewers, and all disagreements will be resolved by discussion with the senior authors (Xueqing Yao) until a consensus be reached. The detailed process of study selection will be displayed in detail in a PRISMA-compliant flow diagram ( ).
(1) The literature including cases of open surgery or hand-assisted LTG; (2) the literature that did not, respectively, provide the data for linear stapler group and circular stapler group or the surgical method was not clearly stated in the literature; (3) the literature was a case report, case series, letters, review or non-control study without control group; (4) the sample size was too small, and the number of cases was less than 20 cases. The studies with fewer than 20 cases are usually considered small-sample studies and were excluded by authors in some published meta-analysis articles. 18 (5) Other treatments were differently performed between two groups during preoperation and postoperation, and these treatments probably affected the observed outcome in the studies; (6) the literature was a repeated publication.
(1) The subjects were the patients who had undergone oesophagojejunostomy in TLTG, and preoperative or postoperative histopathological examination confirmed gastric cancer; (2) according to the different anastomosis methods used for oesophagojejunostomy in digestive tract reconstruction, patients were divided into linear stapling anastomosis and circular stapling anastomosis groups; (3) the study types were randomised controlled trials (RCTs), non-RCTs or observational comparative studies; (4) the original literature should have terms including intraoperative conditions, postoperative specimens, postoperative recovery, postoperative complications, postoperative complications or have at least one of these research data; (5) pooled results can be formulated by the statistical index, such as OR, relative risk or weighted mean difference (WMD); (6) for multiple similar studies from the same research institution, a recent or higher quality study will be selected.
Relevant studies will be searched on PubMed, Cochrane Library, Embase, CNKI and Wanfang Databases in accordance with the population, intervention, control and outcomes criteria from January to July . The studies comparing linear stapler with circular stapler for oesophagojejunostomy in TLTG will be included. The following MeSH terms and their combinations will be searched in (Title/Abstract): (1) &#;linear stapler&#; OR &#;overlap&#; OR &#;FEEA&#; OR &#;functional end-to-end anastomosis&#; OR &#;T-shaped&#; OR &#;π-shaped&#; OR &#;delta-shaped&#;; (2) &#;circular stapler&#; OR &#;OrVil TM &#; OR &#;hemidouble stapling technique&#; OR &#;double stapling technique&#;; (3) &#;totally laparoscopic&#;; (4) &#;total gastrectomy&#;. The related-articles function will be used to increase the search scope, and the computer search will be supplemented with manual screening of the reference lists of all retrieved studies, review articles and conference abstracts.
The protocol of the planned systematic review and meta-analysis was prepared in accordance with the recommendation from the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Protocols statement, 15 and this systematic review and meta-analysis will be written in line with PRISMA statement. 16 In addition, this study protocol was registered with the international prospective register of systematic reviews PROSPERO. 17
Recent decades have witnessed significant advancements in the skills set and the equipment for laparoscopic surgery advance. This has not only expanded the application scope of laparoscopic surgery in gastric cancer,26 27 but has also lead to the transition of laparoscopic reconstruction of the digestive tract in gastric cancer from laparoscopic-assisted surgery to totally laparoscopic surgery.6 However, the application of TLTG for total laparoscopic digestive tract reconstruction faces some difficulties due to its high technical requirements.14 28 However, total laparoscopic digestive tract reconstruction after TLTG has obvious theoretical advantages.29 30 For instance, the pneumoperitoneum provides a larger operation space for surgery and the multiangle lens provides direct vision for operation to avoid damage. Therefore, TLTG is a promising technique for gastric cancer.
It is no doubt that the development of stapler technology has promoted the development of laparoscopic gastrointestinal operation, especially in TLTG. Presently, mechanical anastomosis for oesophagojejunostomy in TLTG is mainly divided into two types: end-to-side anastomosis using the circular stapler and side-to-side/functional end-to-end anastomosis using the linear stapler.6&#;8
The circular stapling anastomosis method is divided into different methods according to the placement of the nail anvil: the traditional method of direct insertion, reverse anvil method and OrVil method.31&#;33 However, in the first two methods, the main body of the stapler cannot enter the abdominal cavity through the trocar, which requires that the pneumoperitoneum be closed and a small auxiliary incision is often created, thereby reducing the fluency and efficiency of the operation. In addition, the difficult in operation of the oesophageal purse suture and the placement of the nail anvil also limits the application of these two methods. Although the OrVil method does not require the placement of an anvil through the abdominal cavity, it requires the services of an anaesthesiologist and a special anvil placement device.9 The price of the special device is high, and the extraction of the guide tube might cause intra-abdominal infection.9 28 34
Linear stapling anastomosis involves functional end-to-end anastomosis (FEEA method) as well as side-to-side anastomosis (Overlap method).35 This technique is appropriate for total laparoscopic gastrectomy compared with using circular stapling anastomosis.11 30 34 Based on the published literatures and the experience of our centre, the linear stapler has the following advantages29 36 37: (1) linear stapler can be easily put into the abdominal cavity via a trocar and has a better visual field; (2) the operation of linear stapler is simple and convenient, and the requirement for the surgeon is lower compared with using a circular stapler; (3) the circular stapler with two rows of staples, but the linear stapler provides three rows of nail technology to theoretically improve the safety of the anastomosis. However, although some advantages have been reported for linear stapler, its application in LTG has some limitations such as8 14 (1) a longer stump of the oesophagus is required which limits the incisal margin; (2) when the anastomosis plane is higher than the plane of oesophageal hiatus, the operation is performed in a narrow thoracic cavity and the visual field is narrowed; (3) the pulling and folding of the jejunum arm might increase the tension in the anastomosis. Whether the possibly increased tension could increase the risk of anastomotic leak is an important topic needed to be resolved in this study. The discussed anastomotic methods have their advantages and disadvantages in the anastomosis of the oesophagus between jejunum, and it is not clear which anastomosis technique is superior.14 Further, no standard methods have been established to guide the selection.38 39 Therefore, it is meaningful and necessary to conduct a systematic review and meta-analysis to provide a reference that could aid clinical surgeons in choosing a more appropriate alternative for their patients.
In this review, in order to collect all existing and available literature, RCTs and non-RCTs as well as observational studies will be included. Because of the novelty of this research topic, a few studies had been reported. However, the non-RCTs and observational studies might affect the quality of the evidence and lower the confidence level of the result. Besides, there are many factors such as different standards of choosing patients, different proficiency in laparoscopic techniques and different habits or methods of using the stapler by different surgeons in different regions, which might influence the results. Hence, in view of these, it is very important for this review to perform subgroup analysis and sensitivity analysis. Further analysis and explanations will be carried out in our review to ensure the robustness and reliability of the results.
In summary, this systematic review and meta-analysis will help to determine the differences in terms of safety and efficacy between linear stapler and circular stapler in TLTG. Furthermore, the findings of this study will not only help the surgeons in choosing the surgical methods, but also might benefit more patients in the future.
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